package q208;

import java.util.TreeMap;

class Trie {

    private class Node{
        public boolean isWord; //到当前节点是否为一个单词
        public TreeMap<Character,Node> next;

        public Node(boolean isWord) {
            this.isWord = isWord;
            next = new TreeMap<>();
        }

        public Node(){
            this(false);
        }
    }

    private Node root;
    private int size;//存储单词数量

    /** Initialize your data structure here. */
    public Trie() {
        root = new Node();
        size = 0;
    }
    
    /** Inserts a word into the trie. */
    public void insert(String word) {
        Node cur = root;
        for (int i = 0 ; i < word.length() ; i++) {
            char c = word.charAt(i);
            if (cur.next.get(c)==null)
                cur.next.put(c, new Node());
            cur = cur.next.get(c);
        }
        //此时cur在word的最后一个字母的位置
        //需要判断这个单词之前在不在Trie中，在的话，size++是不需要执行的
        if (!cur.isWord) {
            cur.isWord = true;
            size++;
        }
    }
    
    /** Returns if the word is in the trie. */
    public boolean search(String word) {
        Node cur = root;
        for (int i = 0 ; i < word.length() ; i++) {
            char c = word.charAt(i);
            if (cur.next.get(c) == null)
                return false;
            cur = cur.next.get(c);
        }
        return cur.isWord;
    }
    
    /** Returns if there is any word in the trie that starts with the given prefix. */
    public boolean startsWith(String prefix) {
        Node cur = root;
        for (int i = 0 ; i < prefix.length() ; i++) {
            char c = prefix.charAt(i);
            if (cur.next.get(c) == null)
                return false;
            cur = cur.next.get(c);
        }
        return true;
    }
}

/**
 * Your Trie object will be instantiated and called as such:
 * Trie obj = new Trie();
 * obj.insert(word);
 * boolean param_2 = obj.search(word);
 * boolean param_3 = obj.startsWith(prefix);
 */